Is it possible to calculate the sole proprietorship income by myself with an excel sheet?

I'm currently searching for software to calculate the tax for freelance but I cannot find one that's free so I was wondering if doing the tax calculations by myself is something that I can do, and if there is a guide somewhere.

I'm doing freelance as a side gig and so I would like to have an idea of how much I will pay in income tax with both my main job and freelance earnings.

by salmix21